Vane pumps are well known and are used in a wide variety of environments. In the automotive field, vane pumps are used in power steering systems, automatic transmission systems and, somewhat more recently, engine lubrication systems amongst others.
While vane pumps provide a number of features and advantages, they do suffer from a disadvantage in that their rotor design and construction has resulted in a rotor assembly diameter which is larger than might otherwise be desired.
This relatively large rotor assembly diameter has prevented the use of vane pumps when insufficient packaging space (i.e.—installation or mounting volume) is available for the pump. Further, as the operating speed of a vane pump is limited to rotational speeds which keep the tip speed of the vanes below the velocity at which the working fluid will cavitate (causing damage and/or excessive wear), the larger the rotor assembly diameter is the slower the maximum speed at which the pump can be operated.